Liquid spring



United States Patent ()fiice 3,431,985 Patented Mar. 11, 1969 3,431,985 LIQUID SPRING John T. Bowen, Princeton, N.J., assignor to Ingersoll- Rand Company, New York, N.Y., a corporation of New Jersey Filed May 27, 1966, Ser. No. 553,485

US. Cl. 173-119 14 Claims Int. Cl. E21b 1/00; E21c 3/00; B25d 9/00 ABSTRACT OF THE DISCLOSURE A liquid spring particularly adapted for use with a rock drill. The spring includes a chamber filled with liquid and a plunger extending into the liquid. The plunger is adapted to be moved toward the chamber by the piston of the rock drill, seal the chamber and compress the liquid in the chamber. The compressed liquid in turn initiates forward movement of the plunger and rock drill piston. Apparatus is provided for re-supplying the chamber with liquid.

This convention relates to a liquid spring device and more particularly to a hydraulic energy storage device which is well adapted for use in high speed reciproeating tools such as a rock drill.

'In prior apparatus of this type, it has been necessary to provide an outside reservoir of fluid under pressure connected to the liquid compression chamber. Also it has been necessary to provide a seal to prevent leakage from the compression chamber to the outside. Since pressure is extremely high, the seal exerts considerable frictional drag on the plunger which results in spring energy loss and seal wear. Additionally, the seals on hydraulic spring means of current design wear out too fast to be of value in tools which deliver repeated impacts such as a rock drill.

It is, therefore, the principal object of this invention to provide a liquid spring means which overcomes th aforementioned disadvantages.

It is another object of this invention to provide a liquid spring for an impact delivering tool which will have longer life.

In general, the above objects are carried out by providing a main body portion having a chamber at one end and a reservoir at the other end. The chamber is sealed at its upper end. There is a plunger mounted for reciprocal movement in said body having one end extending into said chamber and the other end adapted to be struck by a moving mass such as the impacting member of a rock drill. Valve means are provided between the chamber and reservoir adapted to be substantially closed when the plunger moves toward the chamber a predetermined distance. When the valve is closed, the chamber is sealed. Liquid fills the chamber and reservoir. The liquid in the chamber is compressed by the plunger and stops inward movement of the plunger and mass. The compressed liquid stores pressure energy and has enough force to return the plunger to its original position and initiate outward movement of the moving mass. Means are provided for forcing the liquid in the reservoir into the chamber to compensate for loss of liquid in the chamber due to leakage.

These and other objects will become apparent from the following description and drawings in which:

FIG. 1 is a cross-sectional elevation of a portion of a rock drill employing an embodiment of this invention;

FIG. 2 is a section enlarged form taken on the line 22 in the direction of the arrows; and

FIG. 3 is a detail of a portion of FIG. 1 drawn on a larger scale.

In the drawings there is shown a rock drill having a casing 1 and a drill steel 2 slidably mounted in a chuck 3.

An impacting member or piston 4 is mounted for reciprocal movement in a cylinder 5 which is securely mounted in the casing 1. Air under pressure is alternatively supplied to opposite sides of the piston 4 for reciprocating the piston.

In order to advance the piston 4 and deliver an impact to the tool bit 2, fiuid such as air under pressure is supplied to the upper side 6 of the cylinder through an inlet (not shown). To retract the piston 4, air under pressure is supplied to the lower side 7 of the cylinder 5 through a conduit 8 and an inlet 9. Air under pressure in the upper side 6 is exhausted to atmosphere through a port 10.

By this invention there is provided a liquid spring or hydraulic stop means for limiting or stopping the upward movement of the impacting member 4 and initiating its downward movement. Above the cylinder 5 there is a main body A which includes a first housing 20 having a cylindrical bore or reservoir 21 therethrough. The upper portion of the housing 20 is of reduced size, as at 22, in order to threadedly receive a second housing 30 having a high pressure chamber 31. The lower portion of the housing 20 has an end cap 40 received by the bore 21. The cap 40 has a bore 41 therethrough.

A plunger 23 is mounted for reciprocal movement in the reservoir 21. The lower end 25 of the plunger 23 projects out of the bore 41 of the cap 40 into the upper end of the cylinder 5 and is adapted to be contacted by the lower end 11 of the reciprocating member 4. The bore 41 aids in guiding the plunger 23. In some applications where the stroke of the piston 4 is short, it may be desirable to make the plunger 23 and piston 4 one piece.

The upper end of the plunger has a reduced diameter portion 26, which together with the member 20 defines a valve means C, and an enlarged portion 27 which projects into the chamber 31. The upper portion 22 of the housing 20 has a first bore portion 28 which has a female spline portion, clearly shown in FIG. 2, and a second bore portion 29 which is of a size to avoid contact with the plunger 23. The dilference in diameter between the bore 29 and the plunger 23 should be on the order of .001 inch. The bore 28 is only slightly larger than the diameter of the plunger 23, typically .0002 inch, so that the plunger is guided into the bore 29 by the bore portion 28.

The chamber 31 is filled with a liquid such as silicone oil-through an opening 32 which has a sealing plug 33. The cylinder or reservoir 21 is also filled with the same liquid and acts as a reservoir for replacing any liquid which is lost through leakage from the system or leaks back into the reservoir through valve means C.

In operation as the piston 4 moves upward, it contacts the end 25 of the plunger 23. The plunger 23 is moved rapidly inward by the impacting member 4. Until the pretravel gap B, about .010 inch, is closed, thus closing the valve C, little pressure is developed in the high pressure chamber 31. The diiference in size between the bore 29 and plunger 23 is small enough so that little or no leakage occurs when the valve is closed. When the plunger closes the gap B and valve C by reaching the bore 29, the chamber 31 is sealed. Liquid is confined in the chamber 31 and the end 26 of the plunger then compresses the liquid in the chamber 31 since there is no place for it to go. Since liquid will compress only to a slight degree, pressure builds up on the end of the plunger, and upward movement of the plunger 23 and the external mass is stopped after a short distance. This is represented by the dotted line position of the plunger 23 shown in FIG. 1. The compression of the liquid in the chamber 31 will subsequently force the plunger 27 downward to its original position. This downward movement is limited by the end 26 striking the upper portion of the housing in a cushioned manner. The downward movement of the plunger 23 initiates downward movement of the piston 4. When air enters the cylinder 6 to advance the piston 4, the piston is already moving due to the liquid spring of this invention. Thus, a more efficient tool is produced by this invention because the air which operates the piston 4 does not have to start movement of piston 4 from a static position.

Since the liquid used in the high pressure chamber 31 and cylinder 21 is a good lubricant, there will be only a. slight increase in the clearance between the plunger 23 and the bore 28 as operation continues over a prolonged period of time.

Most leakage which does result will be through the clearance between the bore 29 and plunger 23. Should there be leakage, it is compensated for by the liquid in the cylinder 21, thus relieving the necessity of using an outside reservoir and pressure supply. In order to force liquid in the reservoir 21 into the chamber 31, there is provided a piston 24 which sealingly engages the internal side walls of the reservoir 21. The piston 24 has an opening 45 which allows the plunger 23 to move through the piston without moving the piston. When the plunger 23 is in its downward position and valve C is open, the piston 24 will tend to force liquid in the cylinder or reservoir 21 through the splined portion of bore 28 around the plunger 23 and into the high pressure chamber 31 which is, thus constantly filled with liquid. A cut out 44 at the top of the chamber 31 of member 22 is provided to insure communication between the reservoir 21 and the high pressure chamber 31 at all times.

In order to bias the piston upwardly and, thus, force liquid from the reservoir into the chamber 31 and compensate for leakage from the chamber 31 and reservoir 21, a spring 42 may be provided between the cap 40 and the piston 24. Additionally, a port 43 connects the lower side of this piston with the air supply conduit 8. As the piston 24 is biased upwardly, liquid from the make-up cylinder 21 is forced into the high pressure chamber 24. Either or both of the biasing means may be used depending on the leakage and size of the device. The spring 42 allows constant force on the piston while air pressure is applied only during tool operation.

Although this invention has been described for use with a rock drill, it may be used in other high speed reciprocating tools and wherever it is desired to store energy efiiciently for short periods of time. It is intended that this invention not be limited in any way except by that which is within the scope of the appended claims.

I claim:

1. A hydraulic spring device comprising:

a body having a chamber at one end and a reservoir at the other end; a plunger mounted for reciprocal movement in said body and adapted to be moved toward said chamber;

valve means between said chamber and said reservoir for substantially sealing said chamber when said plunger moves toward said chamber a predetermined distance; and

liquid in said chamber adapted to be compressed by said plunger when said chamber is sealed for opposing the movement of said plunger toward said chamber and initiating movement of said plunger away from said chamber.

2. The device of claim 1 wherein said reservoir is filled with liquid and further including means sealingly engaging the side walls of said reservoir for forcing the liquid in said reservoir into said chamber.

3. The device of claim 2 wherein said means for forcing liquid into said chamber includes a piston having a bore therethrough for receiving said plunger and means for biasing said piston toward said chamber.

4. The device of claim 3 wherein said biasing means is a spring.

5. The device of claim 3 wherein said biasing means is air under pressure.

6. The device of claim 3 wherein said biasing means is a spring and air under pressure.

7. The device of claim 1 wherein one end of said plunger always extends into said chamber and the other end of said plunger extends out of said reservoir and is adapted to be contacted by a moving mass.

8. The device of claim 1 wherein said valve means includes a reduced internal wall of said reservoir and said plunger has a close fit in said reduced diameter portion to substantially close said valve after moving a predetermined distance.

9. In combination, a tool for delivering an impact having a casing, a reciprocating impacting member for delivering an impact to a workpiece, means for reciproeating said impacting member, and a liquid spring comprising:

a body having a chamber at one end, a reservoir at the other end mounted within said casing;

a plunger mounted for reciprocal movement in said body and adapted to be moved toward said chamber by said impacting member;

valve means between said chamber and said reservoir for substantially sealing said chamber when said plunger moves toward said chamber a predetermined distance; and

liquid in said chamber adapted to be compressed by said plunger when said chamber is sealed for stopping movement of said plunger and said impacting member.

10. The device of claim 9 wherein said reservoir is filled with liquid and further including a piston sealingly engaging the internal side walls of said reservoir for forcing liquid from said reservoir into said chamber.

11. The device of claim 10 wherein said means for forcing liquid into said chamber includes a piston having a bore therethrough for receiving said plunger and means for biasing said piston toward said chamber.

12. The device of claim 11 wherein said biasing means is a spring.

13. The device of claim 11 wherein said biasing means is air under pressure supplied from said means for reciprocating said impacting member.

14. The device of claim 9 wherein said valve means includes a reduced internal wall of said reservoir and said plunger has a close fit in said reduced diameter portion to substantially close said valve after moving a predetermined distance.

References Cited UNITED STATES PATENTS 2,408,338 9/1946 Parsons 9285 2,678,072 5/1954 Verderber 92-85 3,023,739 3/1962 Dickson et al. 9285 JAMES A. LEPPINK, Primary Examiner.

US. Cl. X.R. 

